The technical field of the invention is lithography and, in particular, methods and materials for advanced lithography using ultraviolet light or particle beams to pattern resist materials.
Generally speaking, xe2x80x9cphotoresistsxe2x80x9d are radiation sensitive films used in lithography for transfer of images to substrates. They can form negative or positive images. Conventional manufacturing of integrated circuits has been enabled by high-performance organic polymeric resists that are spin-coated onto a wafer surface. After coating with a photoresist, the coated substrate is exposed to a source of activating radiation. This radiation exposure causes a chemical transformation in the regions of the coated surface that are exposed. After the radiation exposure step, the photoresist is treated with a developer solution to dissolve or otherwise remove either the radiation-exposed or unexposed areas of the resist coating, depending upon the type of photoresist used.
Resist xe2x80x9coutgassingxe2x80x9d is a concern in advanced lithography and occurs when volatile organic molecules or molecular fragments volatilize from the resist film. This can occur during or after exposure. The outgassing rates for organic resist materials can range from 1010 to 1013 molecules/cm2-sec or higher. This outgassing can cause a reduction in the resist film thickness in the exposed region and/or lead to the deposition of organic molecules on the exposure system. Deposition on the lens of the ultraviolet exposure apparatus can change the optical properties of the lens, ultimately affecting the amount of light transmitted through the lens and the imaging quality. Similarly, degradation of electron-beam lithography performance can occur when outgassing of photoresists during exposure degrades the high vacuum needed for this exposure mode. Because of the highly energetic nature of the radiation source, control of resist outgassing during exposure is of particular importance in UV lithography, especially when sub-200 micrometer (e.g., 193 nm, 157 nm and extreme ultraviolet) wavelengths or particle beams (e.g., e-beams) are used.
Examples of resist materials that outgas are poly-methyl methacrylate, poly-t-butyl methacrylate, and poly-t-butyl acrylate, each of which are commonly used in resist technology. It is believed that the organic molecules released by these resists arise from polymer fragmentation due to absorbed exposure energy (either photon or electron). The polymer fragmentation can be caused either by polymer main chain scission, polymer side chain fragmentation, or polymer blocking group deprotection. The first two are a direct result of photon absorption or electron impact while the latter arises from a chemical reaction of photogenerated acids.
At the longer wavelengths currently used in commercial semiconductor lithography, outgassing is largely caused by the break-up of the photoacid generators (PAGs) present in the photoresist material. Various formulations have been proposed to make PAGs less volatile. However, as the wavelength of the radiation becomes shorter in advanced lithography systems, the polymer backbone of the resist itself becomes a primary source of volatile organic molecules. None of the resist systems proposed to date for advanced lithography systems have addressed the basic problem of outgassing at sub-200 nanometer wavelengths.
A need therefore exists for methods and materials that overcome or reduce the outgassing problem as it effects advanced resist technology.
The present invention pertains to polymeric compositions useful for the suppression or elimination of outgassing of volatile components generated from photoresist polymers during lithographic construction. In resists of the invention, an aromatic compound is mixed with a photoresist composition, such that the aromatic compound suppresses or eliminates outgassing of volatile components upon exposure of the resist to radiation. The aromatic additive is preferably an aromatic polymer and in at least some instances can be substituted with at least one electron-donating group or electron-withdrawing group to enhance its stabilizing effects. In one embodiment, the aromatic compound can be an additive to a resist composition. In another embodiment, the aromatic compound can be incorporated into the polymeric backbone of the resist composition.
The present invention also encompasses methods of lithography based on the surprising discovery that the addition of aromatic compounds can suppress or eliminate the release of volatile by-products generated during advanced lithographic processes. For example, the introduction of poly-p-hydroxystyrene into sub-200 nanometer resist compositions prevents or greatly reduces the release of the volatile by-products. The methods of the invention are applicable to advanced resists formulated for use at sub-200 nm wavelengths, such as 157 nm, as well as extreme ultraviolet (EUV), X-ray and/or particle beam systems.
The features and other details of the invention will now be more particularly described and pointed out by the following specifications and examples. All percentages by weight identified herein are based on the total weight of the photosensitive resist composition unless otherwise indicated. It will be understood that the particular embodiments of the invention are shown by way of illustration and not as limitations of the invention. The principle features of this invention can be employed in various embodiments without departing from the scope of the invention.
From a resist viewpoint, advanced energy sources can be categorized as one of two types. Highly penetrating energy beams, such as X-rays, high-kV electrons, and high-energy particle beams, are only partially absorbed by the resist layer with much of the exposure energy passing into the underlying substrate. On the other hand, highly absorbing energy beams, such as sub-200 nanometer UV radiation, EUV radiation and low-kV electrons, are almost fully absorbed by the resist. Both categories of energy sources, however, exacerbate the outgassing problem.
More specifically, there has been considerable interest recently in the use of shorter wavelengths of light in lithography to achieve finer resolution. Unfortunately, most conventional photoresist materials absorb far (or deep) ultraviolet radiation strongly. This is most pronounced at sub-200 micron UV wavelengths (e.g., at 157 nanometers) and extreme ultraviolet (EUV) wavelengths, where the radiation takes the form of soft X-rays (e.g., at wavelengths of 10 to 20 nanometers). While this is advantageous from the standpoint of resist speed (i.e. the exposure dose required to form a pattern) and the associated printing rate, it poses a problem for projection lithography because of the highly non-uniform absorption of this radiation through the photoresist thickness. In present photoresist materials, EUV radiation will not penetrate much beyond a film thickness of about 0.10 to 0.15 micrometers. Yet, to fabricate holes and other structures in semiconductor materials such as silicon, as well as metals, or dielectrics, the photoresist layer must be thick enough, preferably about 0.5 to about 1.0 micrometers, to withstand etching and/or other processing steps. Accordingly, in order to make use of the increased resolution afforded by advanced lithography systems in the processing and fabrication of small structures, photoresist materials need to address the problem of photonic penetration/etch resistance and yet remain compatible with conventional lithographic processing techniques.
An example of extended optical wavelengths is lithography employing 157 nm ultraviolet radiation. Patterning of resists with 157 nm radiation from an F2 excimer laser represents the next evolutionary step in photolithography. Medium-field, 157 nm systems have already been realized and the first full-field, 157 nm system can be expected in the very near future. Resists for this technology must be capable initially of 100 nanometer resolution and preferably will be extendable to achieve 70 nanometer resolution. Unfortunately, as with the transition to shorter wavelengths in the past, the resist materials developed for longer wavelengths are generally too energy absorbent for practical use as a high resolution, single-layer, resist imageable with 157 nm radiation.
The development of non-novolac based resists was necessary to overcome high novolac absorbance at 248 nm and enable the introduction of 248 nm lithography into IC manufacturing. In a similar manner, 193 nm lithography required the development of new polymer systems to overcome the high 193 nm absorbance of phenolic based polymers. Two different classes of polymers, polyacrylate and polycyclic copolymer based resists were developed, and now compete for predominance in 193 nm lithography. Due to the high absorbance at 157 nm of polyhydroxystyrene, polyacrylate, and polycyclic copolymer based resists, the use of any of these resists is only be possible if the coated resist thickness is under 100 nm. This will place a major strain on the resist to perform outside of its design capabilities.
Resists and polymers behave differently at different wavelengths. This difference in behavior can become dramatic as one moves from 248-nm to 193-nm to 157-nm to even shorter wavelengths for several reasons. In general, the absorbance of the polymer increases as the wavelength is decreased, although the functional groups and degree of conjugation present plays a dominant role in molecular absorptivity. As lithography is extended to 157-nm, photon absorptivity becomes high for most organic polymers.
The effect of photo-absorption on polymers at 157-nm can be quite different than at longer wavelengths. In particular, the photochemistry at 248-nm in 248-nm resists is driven mainly by photoacid generators (xe2x80x9cPAGxe2x80x9d), while at 157-nm it is likely that the resist will have a base polymer that directly undergoes photo-induced transformations such as crosslinking, thus counteracting photoacid induced catalytic deprotection of the polymer.
Polymer photochemistry involves photon absorption, which leads to the production of an excited electronic state of the polymer. If the excitation level is greater than the bond dissociation energy, the excited polymer can dissociate into free radical fragments that can then further react to produce chain scission or polymer crosslinking. The energy associated with specific wavelengths of light increases as the wavelength is decreased, going from 115 to 147 to 182 kcal per mole at 248-nm, 193-nm, and 157-nm respectively. This level of energy can be compared with typical carbon-carbon bond dissociation energies of 90 to 120 kcal per mole. The higher energy associated with 157-nm light consequently leads to an increased excited state population and high quantum yields of photoproducts.
The final photochemical reaction products are dependent on the product of the reaction quantum yield and the amount of absorbed incident dose. The amount of polymer backbone chemistry varies between the 3 lithographic wavelengths, as both higher absorbance and increased quantum yield at lower wavelengths act in concert to yield an increased level of polymer backbone chemistry. The degree in which different resists and polymers respond to this light energy and the pathway in which the photochemical reaction leads, be it chain scission or crosslinking, will greatly influence the ability of resists designed at 248-nm or 193-nm to operate as 157-nm resists.
The following set of equations can then be applied to determine the quantum yield of either polymer chain scission ("PHgr"S) or polymer crosslinking ("PHgr"X). As it is possible that either polymer chain scission or crosslinking or even that concurrent chain scission or crosslinking can occur, the best data fit is determined for each resist or polymer. Either equation 1 or 2 can be used to determine "PHgr"S if no crosslinking is observed. If crosslinking is present, equations 3 and 4 need to be solved simultaneously to determine both "PHgr"S and "PHgr"X. In the equations below, NA is Avogadro""s number and the absorbed dose (D) is determined based on incident dose (I), resist thickness, and the polymer absorption.                               1          /                      M                          n              ,              D                                      =                              1            /                          M                              n                ,                0                                              +                                    Φ              S                        *                          D              /                              N                A                                                                        Equation        ⁢                  xe2x80x83                ⁢        1                                          1          /                      M                          w              ,              D                                      =                              1            /                          M                              w                ,                0                                              +                                    Φ              S                        *                          D              /              2                        ⁢                          N              A                                                          Equation        ⁢                  xe2x80x83                ⁢        2                                          1          /                      M                          n              ,              D                                      =                              1            /                          M                              n                ,                0                                              +                                    [                                                Φ                  S                                -                                  Φ                  X                                            ]                        *                          D              /                              N                A                                                                        Equation        ⁢                  xe2x80x83                ⁢        3                                          1          /                      M                          w              ,              D                                      =                              1            /                          M                              w                ,                0                                              +                                    [                                                                    Φ                    S                                    /                  2                                -                                  2                  ⁢                                      Φ                    X                                                              ]                        *                          D              /                              N                A                                                                        Equation        ⁢                  xe2x80x83                ⁢        4            
Resist outgassing during exposure is problematic with currently available photoresist compositions. Resist outgassing is important both in UV lithography (248 nm, 193 nm, and 157 nm) and in vacuum lithographies such as electron beam.
It has been demonstrated with 248 and 193 nm lithography, that photo-products can outgas and condense on the exposure tool lenses, thus degrading transmission. Specifically, for 193 nm materials, it has been found that haloaromatics compounds are usually the most harmful, followed by aromatic and alkly outgassed photoproducts. Because many volatile organic compounds absorb even more highly at 157 nm, the problem is likely to be more severe at this wavelength and the unique compositions of the invention provide a suitable solution to the problem. Similarly, severe outgassing during e-beam lithography can interfere with the establishment of the high vacuums needed for exposure as well as degrade the tool performance. Again, the unique compositions of the present invention circumvent the disadvantage of currently available resists.
The present invention provides methods to reduce resist outgassing by incorporating into the resist, a material (or materials) that can act as either radical scavengers or have the ability to form stabilizing (or stabilized) radicals. This method is useful for reducing resist outgassing at advanced optical wavelengths such as 193, 157, 100, and 70 nm wavelengths and also with EUV, x-ray, and e-beam exposure sources. The phrase xe2x80x9cextreme ultravioletxe2x80x9d or (EUV) as used herein is intended to include any photonic radiation system operating at a wavelength below about 100 nanometers.
In one embodiment of the invention, a material that can prevent or limit outgassing is poly-p-hydroxystyrene. Other examples of aromatic polymers that can prevent or limit outgassing are poly-p-hexafluoroisopropylstyrene and poly-m-hexafluoroisopropylstyrene. These are just some examples of those polymers that include an aromatic unit. In certain applications, it can be advantageous to use an aromatic polymer that is substituted with at least one electron-donating group. In other applications, an aromatic polymer that is substituted with at least one electron-withdrawing group can be especially advantageous. The aromatic material can be part of a copolymer or terpolymer or multi-component polymer or added as a homopolymer in the presence of other polymers to suppress outgassing. Specific examples of materials that have been shown to reduce or suppress outgassing are described in detail in the experimental section. These materials do not need to completely stop resist outgassing to be useful.
In general, the amount of outgassing suppression agent (the aromatic compound or aromatic polymer) should be sufficient to reduce or eliminate outgassing of the volatile components of the photoresist material during and/or after exposure to radiation. The amount sufficient to accomplish this can be determined by those of ordinary skill in the art and will depend upon such factors as the thickness of the desired film, the photoresist composition, the wavelength of the energy utilized and the amount of energy expended. Analysis of compositions which contain suitable suppressing agents can determine the level of suppressing agent required to reduce or eliminate the outgassing to acceptable levels. This can be accomplished using standard statistical analysis. Generally, the amount of suppressing agent required to reduce or eliminate the outgassing of volatile components is at least 1% by weight of photoresist (solids), preferably between about 5 to about 99%, more preferably from between about 5 to about 95% and most preferably from between about 20 to about 90% by weight. When the suppressing agent is an aromatic compound directly incorporated into the polymer structure of the resist, the aromatic compound can as high as 100 percent of the composition and preferably will constitute between about 1 and 95 percent, more preferably between about 10 and 90 percent, of the polymer.
The term xe2x80x9caromaticxe2x80x9d is well recognized in the art and includes single ring and multiple ring aromatic compounds, e.g., phenyls (aryls) or naphthyls. The term xe2x80x9caromatic polymerxe2x80x9d is likewise well recognized in the art and is intended to encompass polymers having one or more aromatic constituents as either part of the polymer backbone or as a pendant group. The phrase xe2x80x9caromatic unit substituted with at least one electron donating groupxe2x80x9d refers to those compounds, generally polymeric, which are useful for the suppression of outgassing of volatile by-products of resist materials by their ability to donate electrons. The term xe2x80x9carylxe2x80x9d as used herein includes 5- and 6-membered single-ring aromatic groups that can include from zero to four heteroatoms, for example, benzene, pyrrole, furan, thiophene, imidazole, oxazole, thiazole, triazole, pyrazole, pyridine, pyrazine, pyridazine and pyrimidine, and the like. Aryl groups also include polycyclic fused aromatic groups such as naphthyl, quinolyl, indolyl, and the like. Those aryl groups having heteroatoms in the ring structure can also be referred to as xe2x80x9caryl heterocyclesxe2x80x9d, xe2x80x9cheteroarylsxe2x80x9d or xe2x80x9cheteroaromaticsxe2x80x9d. The aromatic ring can be substituted at one or more ring positions with such substituents as described above, as for example, halogen, hydroxyl, alkoxy, alkylcarbonyloxy, arylcarbonyloxy, alkoxycarbonyloxy, aryloxycarbonyloxy, carboxylate, alkylcarbonyl, alkoxycarbonyl, aminocarbonyl, alkylthiocarbonyl, alkoxyl, phosphate, phosphonato, phosphinato, cyano, amino (including alkyl amino, dialkylamino, arylamino, diarylamino, and alkylarylamino), acylamino (including alkylcarbonylamino, arylcarbonylamino, carbamoyl and ureido), amidino, imino, sulfhydryl, alkylthio, arylthio, thiocarboxylate, sulfates, sulfonato, sulfamoyl, sulfonamido, nitro, trifluoromethyl, cyano, azido, heterocyclyl, aralkyl, or an aromatic or heteroaromatic moiety. Aryl groups can also be fused or bridged with alicyclic or heterocyclic rings which are not aromatic so as to form a polycycle (e.g., tetralin).
The term xe2x80x9calkyl groupxe2x80x9d is art recognized and is intended to include hydrocarbon chains, generally having between about one and twenty carbon atoms. Unless the number of carbons is otherwise specified, xe2x80x9clower alkylxe2x80x9d as used herein means an alkyl group, as defined above, but having from one to ten carbons, more preferably from one to six carbon atoms in its backbone structure. Preferred alkyl groups are lower alkyls.
The terms xe2x80x9cheterocyclylxe2x80x9d or xe2x80x9cheterocyclic groupxe2x80x9d refer to 3- to 10-membered ring structures, more preferably 4- to 7-membered rings, which ring structures include one to four heteroatoms. Heterocyclyl groups include pyrrolidine, oxolane, thiolane, oxazole, piperidine, piperazine, morpholine, lactones, lactams such as azetidinones and pyrrolidinones, lactones, sultams, sultones, and the like. The heterocyclic ring can be substituted at one or more positions with such substituents as described above, as for example, halogen, hydroxyl, alkylcarbonyloxy, arylcarbonyloxy, alkoxycarbonyloxy, aryloxycarbonyloxy, carboxylate, alkylcarbonyl, alkoxycarbonyl, aminocarbonyl, alkylthiocarbonyl, alkoxyl, phosphate, phosphonato, phosphinato, cyano, amino (including alkyl amino, dialkylamino, arylamino, diarylamino, and alkylarylamino), acylamino (including alkylcarbonylamino, arylcarbonylamino, carbamoyl and ureido), amidino, imino, sulfhydryl, alkylthio, arylthio, thiocarboxylate, sulfates, sulfonato, sulfamoyl, sulfonamido, nitro, trifluoromethyl, cyano, azido, heterocyclyl, aralkyl, or an aromatic or heteroaromatic moiety. A heteroalkyl moiety is an alkyl substituted with a heteroaromatic group.
The terms xe2x80x9cpolycyclylxe2x80x9d or xe2x80x9cpolycyclic groupxe2x80x9d refer to two or more cyclic rings (e.g., cycloalkyls, cycloalkenyls, cycloalkynyls, aryls and/or heterocyclyls) in which two or more carbons are common to two adjoining rings, e.g., the rings are xe2x80x9cfused ringsxe2x80x9d. Rings that are joined through non-adjacent atoms are termed xe2x80x9cbridgedxe2x80x9d rings. Each of the rings of the polycycle can be substituted with such substituents as described above, as for example, halogen, hydroxyl, alkylcarbonyloxy, arylcarbonyloxy, alkoxycarbonyloxy, aryloxycarbonyloxy, carboxylate, alkylcarbonyl, alkoxycarbonyl, aminocarbonyl, alkylthiocarbonyl, alkoxyl, phosphate, phosphonato, phosphinato, cyano, amino (including alkyl amino, dialkylamino, arylamino, diarylamino, and alkylarylamino), acylamino (including alkylcarbonylamino, arylcarbonylamino, carbamoyl and ureido), amidino, imino, sulfhydryl, alkylthio, arylthio, thiocarboxylate, sulfates, sulfonato, sulfamoyl, sulfonamido, nitro, trifluoromethyl, cyano, azido, heterocyclyl, alkyl, aralkyl, or an aromatic or heteroaromatic moiety.
The term xe2x80x9cheteroatomxe2x80x9d as used herein means an atom of any element other than carbon or hydrogen. Preferred heteroatoms are nitrogen, oxygen, sulfur and phosphorus.
The phrase xe2x80x9celectron donating groupxe2x80x9d is well recognized in the art and refers to those substituents which, due to electronic, inductive, and/or steric effect(s), tend to increase the charge density within the aromatic ring. Such electron donating groups include hydroxyl, amino, substituted or unsubstituted, branched or unbranched alkoxy groups, substituted or unsubstituted amide groups, and substituted or unsubstituted, branched or unbranched alkyl groups. The term xe2x80x9calkoxyxe2x80x9d is well recognized in the art and refers to the basic residue of an alcohol. Similarly, the term xe2x80x9celectron-withdrawing groupxe2x80x9d is well recognized in the art and refers to those substituents which, due to electronic, inductive, and/or steric effect(s), tend to decrease the charge density within the aromatic ring. Such electron-withdrawing groups include esters, ketones, nitrites, and halogen-containing groups. One example of an electron-withdrawing group is a hexafluoroisopropyl group. Preferably, the hexafluoroisopropyl group is located at the para position of a phenyl group.
The resin compositions useful in the invention is nonlimiting, and can be chosen from those resin binder systems currently available to those of ordinary skill in the art. For example, most commercial photoresist formulations, both positive and negative, comprise a film forming resin binder and a radiation sensitive component, e.g., a photo acid generator, (PAG). Suitable examples include, acrylate based polymers, methacrylate based polymers, cycloolefin based polymers, and novalacs.
One class of resists useful in the present invention includes polymeric binders having cyclic structure(s) within the polymer backbone of the general formula: 
where J is a cyclic or bicyclic group and where Y2 and Y3, if present, are each independently hydrogen atoms, alkyl groups, e.g., methyl groups, electron withdrawing groups, e.g., halogen atoms, and a is a positive value from 1 to 100, inclusive, b is a value from 0 to 100, inclusive, and z is a positive value from 2 to 100,000 inclusive. Q is a carboxylic acid, a carbonate or a hydroxyl group. P is a protecting group for a carboxylic acid, e.g., an ester, a carbonate, or a hydroxyl group and T is a covalent bond or a bridging group having the formula: 
wherein Z1 and Z1 are each independently a hydrogen atom, an alkyl group, or an electron withdrawing group and f is a value from 0 to 6. It is understood that there can be more than one T per cyclic or bicyclic group.
The alkyl group can be substituted or unsubstituted, branched or unbranched and can include one or more degrees of unsaturation, e.g., an alkylene or an alkyne group. Suitable substituents include alkyl groups, aryl, esters, amides, amines, carboxylic acid and electron withdrawing groups known in the art. In one preferred embodiment, the alkyl group is a lower alkyl group having between one and five carbon atoms, e.g., a methyl group.
Suitable cyclic and bicyclic groups for J include, but are not limited to, cyclohexyl groups, cyclopentyl, cycloheptyl, and norbomyl. Therefore, suitable monomers include those which include at least one degree of unsaturation within the cyclic or bicyclic structure such that polymerization can occur between reactive monomers.
In addition to the hydroxyl protected polymer and photo-acid generator, small molecules which help to inhibit hydrolysis of the protected hydroxyl groups can be included in the compositions of the invention. These small molecules are typically ester, ether, ketal or acetal protected low molecular weight polyhydridic alcohols or low molecular weight alcohols. Suitable low molecular weight hydrolysis inhibitors include, for example, Di-Boc Bisphenol A, Di-Boc o-cresolphthalein, tert-butyl lithocholate and tert-butyl deoxycholate (available from Midori Kagaku Col, Ltd. Tokyo, Japan).
Phenol-based polymers useful for acid-generating compositions are known and typically include novolak and poly(vinylphenol) resins and copolymers of the same with styrene and/or alpha-methylstyrene. Novolak resins are thermoplastic condensation products of a phenol, a naphthol or a substituted phenol, such as, cresol, xylenol, ethylphenol, butylphenol, isopropyl methoxyphenol, chlorophenol, bromophenol, resorinol, naphthol, chloronaphthol, bromonaphthol or hydroquinone with formaldehyde, acetaldehyde, benzaldehyde, furfural acrolein, or the like. Suitable examples of novolak resins are disclosed in U.S. Pat. Nos. 3,148,983; 4,404,357; 4,115,128; 4,377,631; 4,423,138; and 4,424,315, the disclosures of which are incorporated herein by reference.
Another phenol-based resin for the radiation sensitive compositions of the invention are copolymers of phenols and nonaromatic cyclic alcohols analogous in structure to the novolak resins and the poly(vinylphenol) resins. Such copolymers provide radiation sensitive compositions with relatively greater transparency to activating radiation. These copolymers can be formed in several ways. For example, in the conventional preparation of a poly(vinylphenol) resin, a cyclic alcohol can be added to the reaction mixture during the polymerization reaction which is thereafter carried out in normal manner. The cyclic alcohol is preferably aliphatic, but can contain one or two double bonds. The cyclic alcohol is preferably one closest in structure to phenol. For example, if the resin is poly(vinylphenol), the comonomer would be vinyl cyclohexanol.
Poly(vinylphenol) resins are thermoplastic polymers that can be formed by block polymerization, emulsion polymerization or solution polymerization of the corresponding monomers in the presence of a cationic catalyst. Vinylphenols useful for the production of poly(vinylphenol) resins can be prepared, for example, by hydrolysis of commercially available coumarin or substituted coumarins, followed by decarboxylation of the resulting hydroxy cinnamic acids. Useful vinylphenols can also be prepared by dehydration of the corresponding hydroxy alkyl phenols or by decarboxylation of hydroxy cinnamic acids resulting from the reaction of substituted or non-substituted hydroxybenzaldehydes with malonic acid. Alternatively, polyvinyl phenol resins can be prepared by the direct polymerization of vinylphenol or by polymerizing acetoxy blocked vinyl phenol.
Other resins suitable for the practice of the invention include polymers made from polystyrene maleimides with pendant acid labile functionalities. Examples of useful polymers include those disclosed in U.S. Pat. Nos. 4,931,379, and 4,939,070, both of which are incorporated herein by reference. Vinylic polymers containing recurrent pendant group are also useful and are disclosed in U.S. Pat. No. 4,491,628, incorporated herein by reference.
Another suitable resin is polyglutarimides, prepared according to U.S. Pat. No. 4,246,374, incorporated herein by reference which are soluble in aqueous base and contain at least 40 weight percent of the nitrogen atoms of the NH or ammonia form.
Yet other suitable resin binders for use in accordance with the invention are phenol-based polymers that are partially silylated. For example, a silylated polymer is disclosed in. U.S. Pat. No. 4,791,171, the contents of which are incorporated herein by reference. This patent discloses partially silylated poly(vinylphenol) polymers prepared by derivatizing the phenolic hydroxide moieties of a poly(vinylphenol) with suitable organosilicon compounds. Such derivatization can be accomplished, for example, by condensation of a poly(vinylphenol) with an organosilicon compound that has a suitable leaving group, for example trimethylsilylmethylchloride, bromide, mesylate or tosylate; trimethylsilylchloride, bromide, cyanide or mesylate; phenyldimethylsilylchloride; or t-butyldimethylsilylchloride.
Generally, the alkali-soluble resin containing phenolic hydroxyl groups useful in the present invention can be copolymers of o-, m-, or p-hydroxystyrene or o-, m-, or p-hydroxy-alpha-methylstyrene in which the content of the styrene derivative, for example, can be at least 30 mol %, preferably at least 50 mol %, a homopolymer of any of these styrene derivatives, or a partially hydrogenated resin derived from the copolymer or homopolymer. Preferred examples of comonomers usable for the above copolymer include acrylic esters, methacrylic esters, acrylamide and analogues thereof, methacrylamide and analogues thereof, acrylonitrile, methacrylonitrile, maleic anhydride, styrene, .alpha.-methylstyrene, acetoxystyrene, and alkoxystyrenes. More preferred are styrene, acetoxystyrene, and t-butoxystyrene.
In certain embodiments the suppression agent is incorporated into the resist polymeric resist, e.g., a copolymer, tripolymer, or terpolymer. Such polymeric compositions can be prepare by standard methods known in the art such as by condensation reactions, radical addition reactions, emulsion polymerization, block polymerization, etc. Suitable examples include t-BOC p-hydroxy styrene/p-hydroxy styrene copolymers, t-butyl acrylate/p-hydroxy styrene copolymers or t-butylacrylate/p-hydroxystyrene/styrene terpolymers
Specific examples of the photosensitive organic halogen compound include halogen-substituted paraffinic hydrocarbons such as carbon tetrabromide, iodoform, 1,2,3,4-tetrabromobutane and 1,1,2,2-tetrabromoethane; halogen-substituted cycloparaffinic hydrocarbons such as hexabromocyclohexane, hexachlorocyclohexane and hexabromocyclododecane; halogen-containing s-triazines such as tris(trichloromethyl)-s-triazine, tris(tribromomethyl)-s-triazine, tris(dibromomethyl)-s-triazine and 2,4-bis(tribromomethyl)-6-methoxyphenyl-s-triazine; halogen-containing benzenes such as (bis(trichloromethyl)benzene and bis(tribromomethyl)benzene; halogen-containing sulfone compounds such as tribromomethylphenylsulfone, trichloromethylphenylsulfone and 2,3-dibromosulforane; and halogen-substituted isocyanurates such as tris(2,3-dibromopropyl)isocyanurate.